3 way diverting valves versus 3 way mixing valves 6

[rossc]

3 way mixing valves are common. 3 way diverting valves are not. In the past I had encountered an owner you vowed to stay away from diverting valves but it appeared that the real issue was that the diverting valve was applied in a mixing valve application

Has anyone consistently relied on diverting valves for an HVAC application?

 

[RossABQ]

Do you mean 3-way control valves, as in an AHU coil temperature control valve? They were very common on constant volume chilled water/heating water systems.

 

[AbbyNormal]

Usually see the diverting valve in chilled water. With hot water you can modulate the supply water temp to a coil to modulate capacity, chilled water divert the flow to reduce capacity.

Take the "V" out of HVAC and you are left with a HAC(k) job.

 

[AbbyNormal]

or you pipe the mixing valve to divert or the diverting valve to mix

Take the "V" out of HVAC and you are left with a HAC(k) job.

 

[quark]

rossc,

Put a 3 way controlling valve in supply line and it gets the name diverting valve and put it in return line and it becomes a mixing valve.

The main issue is to keep the coil full.

 

[lilliput1]

3 way mixing valves design is diferent from that of 3 way diverting valve so the valve plug will seat against the flow. Proper flow direction would be cast on each valve to not allow them to be used interchangebly. In a 3 way mixing valve the flow from the bottom (normally open) & a side port (normally closed) are both directed out to the opposite side, common port. In a 3 way diverting valve, the flow from the common side port is directed out to either the bottom port (normally open) or the opposite side port (normally closed).

 

[RossABQ]

I agree with lilliput1's explanation that you can't use one type for the other. His flow descriptioons are exactly right.

In my experience, by far the most common HVAC coil application for 3-ways is the (diverting) coil temperature control valve. In this application the bottom port is the line to return (bypass flow) and the through-flow (opposite from inlet) is flow to the coil. This is especially common at the end of a heating water run (furthest end from source), even on VFD controlled systems, because it provides a minimum flow to keep the lines warm (by bypassing only when there is no coil demand).

So I would answer the original question by saying that diverting valves are very common, if not the rule, in HVAC applications.

 

[AbbyNormal]

Mixing valve can be thought of as two inlets and one outlet, diverting valve one inlet and two outlets.

How you pipe them makes a difference

Take the "V" out of HVAC and you are left with a HAC(k) job.